Hermetic packages for semiconductor devices are typically ceramic packages sealed with caps or lids using glass or metal seals. Hermetic sealing is employed to prevent entry into the package of undesirable chemicals which could damage the semiconductor device contained therein. However, the presence of moisture, even in very small or trace amounts, within the hermetic package can also damage the semiconductor device. To avoid any damage to the semiconductor device from moisture contained within the package after hermetic sealing, it is necessary to have the moisture content less than 5000 ppm, otherwise moisture induced corrosion failure of the semiconductor device may result.
One of the sources of moisture in the package can be the inorganic adhesive used to attach the semiconductor device to a substrate. To avoid the possibility of introducing moisture to the package from the adhesive, inorganic adhesive such as silver filled glass paste have been used. These adhesives do not release moisture upon heating for curing. However, common die attach adhesive containing polymers, epoxy, polyimide, etc., give off moisture upon heating for curing and therefore cannot be used where low moisture conditions within the hermetic package are required.
The present invention provides a method of reducing the water moisture content in a hermetic package containing a semiconductor device to prevent damage to the semiconductor.